Heterocyclic phosphorus compounds as stabilizers for poly-alpha-olefins



United States Patent 3,422,058 HETEROCYCLIC PHOSPHORUS COMPOUNDS ASSTABILIZERS FOR POLY-ALPHA-OLEFINS Carl C. Greco, Bronx, N.Y., assignorto Stautfer Chemical Company, New York, N.Y., a corporation of DelawareNo Drawing. Original application Oct. 23, 1965, Ser. No. 504,244.Divided and this application Dec. 5, 1967, Ser. No. 703,502 US. Cl.Z60-45.8 3 Claims Int. Cl. C081? 45/60; C07f 9/16 ABSTRACT OF THEDISCLOSURE Poly-a-olefin compositions having improved light stability.The compositions comprise an tit-Olefin polymer formed by thepolymerization of an u-mono-olefinic aliphatic hydrocarbon having from 2to 10 carbon atoms and a stabilizing quantity of a novel heterocyclicdiphenylphosphinodithioate of the general formula:

X fi @e- 2 \SJ wherein X is a substituent selected from the groupconsisting of hydrogen, lower alkyl, lower alkoxy and a halogen; and Yrepresents the atoms necessary to complete a heterocyclic ring selectedfrom the class consisting of thiazole, thiazoline, thiazolidine, andbenzathiazol wherein each ring may be substituted with one or moresubstituents selected from the group consisting of lower alkyl, loweralkoxy, and halogen.

This application is a division of application No. 504,244, filed Oct.23, 1965.

This invention relates to novel organophosphorus esters. Moreparticularly, this invention is concerned with novel heterocyclicdiphenylphosphinodithioates which are useful as light (ultra-violet)stabilizers for poly-alphaolefin compositions.

It is known that plastic and polymeric materials generally undergodegradation in the presence of light and/ or heat. Especially sensitiveto these agencies are some of the synthetic resins such as polyethylene,polypropylene and the like. In order to increase the life of plasticsand polymers, it has become the practice to incorporate therein certainsubstances, usually referred to as ultra-violet absorbers which arecapable of absorbing the incident actinic radiation, thereby protectingthe plastic substrate from deterioration.

We have now discovered that certain novel heterocyclicdiphenylphosphinodithioates are effective in protectingpoly-alpha-olefins against the deleterious effects of light, and theprovision of such compounds constitutes the primary purpose and objectof this invention.

Another object of the invention is to provide polyalpha-olefincompositions stabilized with the above-named compounds.

Other objects will be apparent from the detailed description whichfollows.

The noyel heterocyclic diphenylphosphinodithioates of the invention maybe represented by the general formula represents the atoms necessary tocomplete a heterocyclic ring selected from the class consisting ofthiazole, thia- 3,422,058 Patented Jan. 14, 1969 wherein X and Y are aspreviously defined.

In preparing the new organo phosphorus esters of the invention, I havediscovered that generally excellent results are achieved by heating thediphenylphosphinothioic chloride with a heterocyclic mercaptan with orwithout a solvent and thereafter isolating the heterocyclicdiphenylphosphinodithioate from the hydrochloric acid by-product. Anespecially convenient means for conducting the reaction is to reflux thecomponents in the presence of a relatively inert organic solvent such asbenzene, toluene or xylene. The use of a tertiary amine such aspyridine, alphaapicoline or quinoline to act as a hydrogen halideacceptor is also desirable. After removing the amine hydrochlorideprecipitate and distilling off the solvent under reduced pressure, theresidual heterocyclic diphenylphosphinodithioate may be isolated byemploying the usual techniques available to the skilled organic chemistsuch as crystallization, distillization, sublimation and the like.

The ultra-violet stabilizer compounds contemplated by the invention maybe blended or incorporated into the poly-alpha-olefin compositions byany of the conventional methods commonly used for mixing such materialswith resins and plastics. For example, milling on heated rolls,deposition from solvents and dry blending are applicable well-knowntechniques.

In order to prepare poly-alpha-olefin compositions which are resistantto prolonged exposure to sunlight and the elements, it is preferred thatthe concentration of the novel heterocyclic diphenylphosphinodithioatebe maintained in the range of 0.01 to about 5.0% based on the weight ofthe polymer.

Although the molecular weight of poly-alpha-olefins varies over widelimits, the compounds of the invention are not restricted to anyparticular molecular weight range. Poly-alpha-olefins ranging inmolecular weight from about 15,000 to about 20,000, however, areafforded particularly excellent protection.

The following examples which are illustrative of the invention shouldnot be construed as limiting examples, for variations and modificationsthereof will be apparent to one having ordinary skill in this art.

PREPARATION OF THE COMPOUNDS Example 1.--2-thiazolin-2-yldiphenylphosphinodithioate s N-CH 1| 1 F-S- CH2 In a 250 cc. flashfitted with a stirrer, condenser, thermometer and dropping funnel wasplaced 9.5 grams (0.08 mol) of Z-mercaptothiazoline, 10 cc. of pyridineand cc. of benzene. The mixture was heated to 80 C. and grams (0.08 mol)of diphenyl phospinothioic chloride was added by way of the droppingfunnel. The reaction mixture was refluxed for four hours and thenallowed to stand at room temperature for one day. After removing thepyridine hydrochloride precipitate by filtration, the filtrate wasdistilled at reduced pressure to remove the solvent. The residualcolorless solid was crystallized from benzene. Infrared spectrumanalysis indicated the purified product to have the above depictedconfiguration.

Example 2.--2-benzothiazolyl diphenylphosphinodithioate In a 250 cc.flask fitted with a stirrer, condenser, thermometer and dropping funnelwas placed 5.6 grams (0.36 mol) of Z-mercaptobenzothiazolyl, 8 cc.pyridine and 125 cc. toluene. The mixture was heated to 95 C. andmaintained at the temperature for five hours. After standing overnight,the pyridine hydrochloride precipitate was separated by filtration andthe filtrate was distilled at reduced pressure to remove the solvent.The residual solid was crystallized from acetonitrile. Infrared spectrumanalysis indicated the purified product to have the above depictedconfiguration.

Using the procedure of Examples 1 and 2, the following compounds may beprepared:

3.--4-benzyl, S-ethyl, Z-thiazolyl diphenylphosphinodithioate Example 4.4,5-dimethyl, 2-thiazolidinyl bis(p-chlorophenyl)-phosphinodithioateExample Example 5.--4,5-dichlor0, 2-thiazolidinyldiphenylphosphinodithioate II 11 s NCCl Example 6.2-thiazolyldiphenylphosphinodithioate Example 7.-4-ethoxy, S-chloro, 2-thiazolinylbis(pethoxyphenyl) phosphinodithioate Example 8.-2-thiazolinylbis(p-n-propyldiphenyl)phosphinodithioate S N-CH2 (CH (CH) i s ("3 011 az z-- 4 Dry blends consisting of 0.5% by weight of each of the compoundsof Examples 1 and 2 and grams of isotactic polypropylene were subjectedto compression molding in the usual manner at a temperature of 400 F.for six minutes at 2000 p.s.i. The blended polymers were compressionmolded or extruded into 25 mil. sheets and thereafter cut into squaresamples measuring 2 inches on the side. A like sample containing nostabilizer was also prepared and tested. The samples were then exposedin a xenon are weatherometer operating at 6000 watts. The water cyclewas adjusted whereby each sample was subjected to 18 minutes of waterspray and 102 minutes of dry exposure for each two hours of exposure.Exposure damage to the samples of polypropylene was assessed withrespect to change of structural strength.

After a period of exposure in excess of 1050 hours, the tests sheets ofpolypropylene showed no signs of brittleness when flexed at an angle ofNor was there any evidence at this time of any surface crazing or anycoloration or staining. A blank specimen of unstabilized polypropylenewhich was exposed concurrently with the stabilized product failed thefiexure test after 250 to 300 hours exposure time.

The weatherometer as used in compiling the data and tests describedherein was purchased from the Atlas Electric Devices Company, Chicago,Ill. The instrument is identified as a 6000 watt xenon arc weatherometerModel 60W.

The polypropylene resin as used in the above-described example is anunstabilized general purpose, high molecular weight polypropylene of theisotactic or crystalline type. Typically, it has a melt index of 4 at230 C. and a specific gravity of 0.905. The resin is supplied in theform of natural flakes. We have also used other commercially availablegrades of unstabilized isotactic polypropylene resin. The resultsobtained in using the various grades and types of polypropylene were ingeneral agreement.

I claim:

1. A solid poly-alpha-olefin composition having improved stabilitytoward light degradation which comprises an alpha-olefin polymer formedby the polymerization of an alpha-mono-olefinic aliphatic hydrocarbonhaving from 2 to 10 carbon atoms and a stabilizing quantity of a novelheterocyclic diphenylphosphinodithioate of the general formula ll @a -aY S) wherein X is a substituent selected from the group consisting ofhydrogen, lower alkyl, lower alkoxy and a halogen; and Y represents theatoms necessary to complete a hererocyclic ring selected from the classconsisting of Z-thiazolyl, 2-thiazolin-2-yl, Z-thiazolidinyl, andZ-benzothiayolyl wherein each ring may be substituted with one or moresubstituents selected from the group consisting of lower alkyl, loweralkoxy, and halogen.

2. A solid poly-alpha-olefin composition according to claim 1 havingimproved stability toward light degradation which comprises solidpolypropylene and a stabilizing amount of 2-thiazolin-2-y1diphenylphosphinodithioate.

3. A solid poly-alptha-olefin composition according to claim 1 havingimproved stability toward light degradation which comprises solidpolypropylene and a stabilizing amount of 2-benzothiazolyldiphenylphosphinodithioate.

References Cited UNITED STATES PATENTS 3,335,108 5/1967 Pines 260-453DONALD E. CZAJA, Primary Examiner.

M. I. WELSH, Assistant Examiner.

US Cl. X.R.

